JPH03131104A - Voltage controlled oscillator - Google Patents

Abstract

PURPOSE:To easily correct the dispersion in a frequency modulation sensitivity with external voltage control when an oscillating frequency of an oscillator is occasionally largely changed by inserting additionally one varactor diode whose capacitance is changed by the electronic tuning to the usual sub resonance mode. CONSTITUTION:A main resonance mode 20 consists of a dielectric resonator 6, a capacitor 4, and a trimmer capacitor 5, and a sub resonance mode unit 21 comprises varactor diodes 1, 3, a capacitor 2, and an inductor 9. The oscillating frequency depends nearly on the main resonance mode 20. The modulation characteristic varies with the sub resonance mode 21, especially with the rate of change in the capacitance of the varactor diode 1. The varactor diode 3 is used to correct the rate of capacitance change in the varactor diode 1. That is, when the modulation sensitivity is too high, a large reverse bias voltage is given to the varactor diode 3, which is operated to suppress the capacitance change in the sub resonance mode due to a change in the varactor diode 1 resulting from the smaller capacitance.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a voltage controlled oscillator, and in particular to a microwave band oscillator that changes the oscillation frequency over a wide band, the present invention relates to a voltage controlled oscillator that can easily correct variations in frequency modulation sensitivity. Regarding oscillators.

[Conventional technology]

Conventionally, this type of voltage controlled oscillator compensated for variations in modulation sensitivity by replacing the capacitor inserted in series with the variable capacitance diode used for frequency modulation, or by changing the length of the strip line. .

[Problem to be solved by the invention]

The conventional voltage-controlled oscillator described above has a configuration in which the resonance mode of the dielectric resonator is the main resonance mode, and the resonance mode composed of variable capacitance diodes, strip lines, etc. is the sub-resonance mode. When changing the oscillation frequency, since the main resonant mode is changed, the correlation with the sub-resonant mode changes, resulting in large variations in frequency modulation sensitivity. Another disadvantage is that it requires delicate adjustments and man-hours to make the sub-resonant mode follow changes in the main resonant mode by manually replacing the capacitor connected in series with the variable capacitance diode and changing the length of the strip line. be.

[Means to solve the problem]

The voltage controlled oscillator of the present invention includes a main resonance mode oscillation circuit having an oscillation transistor, a dielectric resonator coupled to the oscillation transistor, and a trimmer capacitor, and at least two main resonant mode oscillation circuits each having a capacitance changed by an externally applied reverse bias voltage. The oscillation frequency is adjusted by the trimmer capacitor of the main resonance mode oscillation circuit, and the varicapacitance diode of the sub-resonance mode oscillation circuit is reverse biased. Modulation sensitivity is adjusted by voltage.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention. The embodiment shown in FIG. 1 includes variable capacitance diodes 1 and 3, capacitors 2, 4, and 7, whose capacitance can be varied by external electronic tuning.
It is composed of a dielectric resonator 6, a high frequency trimmer capacitor 5 whose capacitance is changed mechanically from the outside, for example, and an oscillation transistor 8. Note that the main resonance mode 20 is formed by the dielectric resonator 6, the capacitor 4, and the trimmer capacitor 5,
The sub-resonance mode 21 is formed by a variable capacitance diode 1°3, a capacitor 2, and an inductance 9. Here, the oscillation frequency is almost determined by the main resonance mode 20, and the oscillation frequency can be changed greatly by the trimmer capacitor 5. The modulation characteristics change in the sub-resonant mode 21, and in particular, change depending on the rate of change in the capacitance of the variable capacitance diode 1. The variable capacitance diode 3 is inserted to correct the rate of change in capacitance of the variable capacitance diode 1.

The characteristic diagrams (a) and (b) in FIG. 2 show the modulation characteristics when the variable capacitance diode 1 is biased from the outside and the voltage is varied. FIG. 1(a) shows that the center oscillation frequency fol is changed to the center oscillation frequency f02 by the trimmer capacitor 5.
The modulation characteristics 22 and 23 are shown when the capacitance of the variable capacitance diode 3 for rate of change correction is fixed and the modulation voltage applied to the variable capacitance diode 1 is changed.

Figure 2(b) shows the state of fol in Figure 2(a) when a bias voltage is applied to the variable capacitance diode 3 for rate of change correction to increase the capacitance and the voltage applied to the variable capacitance diode 1 is changed. This shows that almost the same characteristic as the modulation characteristic 24 in the f02 state was obtained.In other words, if the modulation sensitivity is too large, a large reverse bias voltage is applied to the variable capacitance diode 3, and the capacitance is is made small, and operates to suppress the capacitance change in the sub-resonant mode due to changes in variable capacitance diode 1. Conversely, if the modulation sensitivity is too small, a small reverse bias voltage is applied to variable capacitance diode 3 to correct the modulation sensitivity. can do.

〔Effect of the invention〕

As explained above, the present invention provides frequency modulation when the oscillation frequency of the oscillator is mechanically significantly changed by inserting one more variable capacitance diode whose capacitance changes by electronic tuning into the normal sub-resonant mode. Variations in sensitivity can be easily corrected by external voltage control. Therefore, when it is necessary to change the oscillation frequency over a wide band, the modulation characteristics can be kept almost constant using the same resonator and only by external voltage control, which eliminates the need to replace parts as in the conventional case. It has the effect of reducing man-hours.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 (a>, (
b) is a characteristic diagram of this example. 1.3...Variable capacitance toiode, 2.4.7...Capacitor, 5...High frequency trimmer capacitor, 6...
- Dielectric resonator, 8... Transistor, 9... Inductance, 20... Main resonance mode, 21... Sub-resonance mode, 22-25... Modulation characteristics.

Claims (1)

[Claims] A main resonance mode oscillation circuit having an oscillation transistor, a dielectric resonator coupled with the oscillation transistor, and a trimmer capacitor, at least two variable capacitance diodes whose capacitances are changed by an externally applied reverse bias voltage, and a strip line. A sub-resonant mode circuit having an inductance of A voltage controlled oscillator featuring: